Circuit for a transponder and method for testing the circuit

1. A method for testing a circuit for a transponder, the method comprising: operating the circuit in a passive mode such that a first interface of the circuit is supplied with energy from a field, wherein at least one switchable terminal comprising a second interface of the circuit is deactivated while energy from the field is supplied via the first interface; receiving, via the field, a command by the circuit during the passive mode, the command configured to activate a test routine code, the command causing a branch address pointing to the test routine code to be loaded in a branch register to activate the test routine code; responsive to the branch address, activating the test routine code; storing a first test data, generated by the test routine code, and a first session number identifying the first test data, in a memory area of a memory of the circuit, the memory area being predetermined by the test routine code; storing a second test data, generated by the test routine code, and a second session number identifying the second test data, in the memory area; and after receiving a subsequent request for the first and second test data, transmitting during the passive mode the first test data and the first session number, together with the second test data and the second session number, during one return transmission via the field.

2. The method according to claim 1 , wherein the test routine code is received during a first communication, and wherein the test routine code is activated in a second communication thereafter.

3. The method according to claim 1 , wherein the predetermined memory area for storing the first and second test data is changed or programmed by changing the test routine code.

4. The method according to claim 1 , wherein the circuit is operated with a clock signal from an internal clock generator of the circuit or with a clock signal derived from a carrier signal of the field to execute the test routine code.

5. The method according to claim 1 , wherein, within a communication protocol between a base station connectable by the field and the circuit of the transponder, a time slot is agreed upon for transmission of the first and second test data and the first and second session numbers from the circuit of the transponder to the base station.

6. The method according to claim 1 , wherein the first and second test data are encrypted for storage.

7. The method according to claim 1 , wherein an authentication is carried out by the circuit of the transponder for activation of the test routine code.

8. A method for testing a circuit for a transponder, the method comprising: operating the circuit in a passive mode such that the circuit is supplied with energy from a field; receiving a command by the circuit during the passive mode, via the field to activate a test routine code, the command causing a branch address pointing to the test routine code to be loaded in a branch register to activate the test routine code; storing a first test data, generated by the test routine code, and a first session number identifying the first test data, in a memory area of a memory of the circuit, the memory area being predetermined by the test routine code; storing a second test data, generated by the test routine code, and a second session number identifying the second test data, in the memory area; responsive to the branch address, activating the test routine code; and transmitting during the passive mode the first test data and the first session number, together with the second test data and the second session number, during one return transmission via the field, wherein, within a communication protocol between a base station connectable by the field and the circuit of the transponder, a reserved time slot is agreed upon for transmission of the first and second test data and the first and second session numbers from the circuit of the transponder to the base station, wherein the circuit of the transponder transmits the first and second test data and the first and second session numbers to the base station during the reserved time slot that was agreed upon.

9. A circuit for a transponder, the circuit comprising: a first interface configured to communicate via a field; at least one switchable terminal comprising a second interface of the circuit; a processor unit connectable to the first interface; and a memory connectable to the processor unit, wherein the processor unit, in a passive mode, is supplied with energy from the field, wherein the first interface and the processor unit are configured to receive via the field, when in passive mode, a command to activate test routine code, the command causing a branch address pointing to the test routine code to be loaded in a branch register, wherein the processing unit is configured by the branch register to activate the test routine code, wherein the processor unit is configured to store a first test data, generated by the test routine, and a first session number identifying the first test data, in a memory area of the memory predetermined by the test routine and to store a second test data, generated by the test routine, and a second session number identifying the second test data, in the memory area; and wherein the first interface and the processor unit are configured to transmit the first test data and the first session number, together with the second test data and the second session number, during one return transmission via the field when in the passive mode after receiving a subsequent request for the first and second test data, wherein, during the passive mode, the at least one switchable terminal of the circuit is deactivated while energy from the field is supplied via the first interface.

10. The circuit according to claim 9 , wherein the processor unit is configured to: store the test routine code in response to a first communication that is received; and activate the test routine code in response to a second communication that is received after the first communication.

11. The circuit according to claim 9 , wherein the memory area that is for storing the first and second test data is changed or programmed by changing the test routine code.

12. The circuit according to claim 9 , wherein the circuit is operated with a clock signal from an internal clock generator of the circuit or with a clock signal derived from a carrier signal of the field to execute the test routine.

13. The circuit according to claim 9 , wherein the first and second test data are encrypted for storage.

14. The circuit according to claim 9 , wherein an authentication is carried out by the circuit of the transponder for activation of the test routine code.

15. A circuit for a transponder, the circuit comprising: an interface configured to communicate via a field; a processor unit connectable to the interface; and a memory connectable to the processor unit, wherein the processor unit, in a passive mode, is supplied with energy from the field, wherein the interface and the processor unit are configured to receive via the field, when in passive mode, a command to activate a test routine code, the command causing a branch address pointing to the test routine code to be loaded in a branch register, wherein in response to the branch address the processing unit is configured to activate the test routine code, wherein the interface and the processor unit are configured to transmit a first test data generated by the activated test routine, and a first session number identifying the first test data, via the field when in the passive mode, wherein the interface and the processor unit are configured to transmit a second test data generated by the activated test routine, and a second session number identifying the second test data, via the field when in the passive mode, wherein, within a communication protocol between a base station connectable by the field and the circuit of the transponder, a reserved time slot is agreed upon for transmission of the first test data and the first session number, together with the second test data and the second session number, from the circuit of the transponder to the base station, and wherein the interface and the processor unit are configured to transmit the first and second test data and the first and second session numbers, during one return transmission during the reserved time slot that was agreed upon.